Plague is a disease that has been present for thousands of years and described since the earliest medical accounts. It is present today even in developed countries, and may present in a variety of forms. Bubonic disease, pneumonia, and sepsis are seen in addition to a number of other less common manifestations. As an agent of bioterrorism, an aerosol Y pestis would pose an imminent threat if released in the appropriate environment. Diagnosis can be made with readily available techniques, but laboratory handling of specimens requires special care. Treatment should be instituted immediately when there is a strong suspicion of plague, as delaying therapy will result in increased morbidity and mortality.